1. Field of the Invention
This invention relates generally to test equipment for monitoring and troubleshooting various electrical and electromechanical systems in an automotive vehicle.
2. Description of the Related Art Including Information Disclosed Under 37 CFR .sctn..sctn.1.97-1.99
The invention relates more particularly to a unique in-line test module for verifying the presence of proper signal levels generated by an electronic control module (ECM) of a vehicle, as well as for verifying the operativeness of the accessory equipment controlled thereby; in addition, the unique test module provides information relating to the electrical connections existing between the ECM and such equipment, as for example the integrity of the interconnecting wiring harness, connectors associated therewith, etc.
Within the past five years or so, many automobile manufacturers have devised various types of on-board computers that perform a variety of functions ranging from providing control signals that regulate the operation of the vehicle engine and monitor its functioning, to controlling and sensing the operation of various electrical and electromechanical systems of the vehicle. As vehicles became more sophisticated, the on-board computers have been increasingly called upon to perform additional functions, such as those associated with control of anti-pollution equipment, heater or air conditioner devices, and a multitude of other tasks that involve electrical or electromechanical control.
In order to assist service personnel in troubleshooting, many manufacturers have incorporated a diagnostic receptacle connected to the on-board computer, which receptacle can accept a mating receptacle from suitable diagnostic equipment that is specially designed to communicate with the on-board computer. Information is thereby exchanged between the computer and the diagnostic equipment, to isolate areas exhibiting malfunctions or erratic symptoms. Various degrees of sophistication have been employed. One drawback in many of the systems recently devised is that a particular piece of diagnostic equipment may be suitable for use only with selected vehicle models manufactured during a single model year. To the best of my knowledge, up to the present time, little effort has been made to standardize the test equipment or to establish guidelines that would enable such equipment to be universal, and to be capable of employment with vehicles manufactured by different companies, for example.
Typical diagnostic systems currently in use are described in an April, 1986 issue of Motor Magazine, entitled ELECTRONIC TECHNICIANS, pages 45-54. In both of the systems described, a test computer is connected to the automobile's electronic control module (ECM), and the service technician can punch a series of keys to perform checks on a number of the vehicle's operating systems. One arrangement permits the technician to communicate directly with the manufacturer's facility in Detroit. As noted above, one of the problems with such systems is that they are not interchangeable with one another; each manufacturer has devised his own design and the designs are generally limited to use with vehicles made only within the last 3-5 years, and on specific models.
An alternate approach is one adopted by a firm known as Concept Technology, Inc. of Birmingham, Michigan. The apparatus they manufacture is described in an advertising bulletin identified by the number 102-0586, dated 1986. In the disclosed system, a test probe interface module is connected between the vehicle's electronic control module (ECM) and the wiring harness. A "jack box" is provided, having multiple insulated terminals that can be selectively touched by a test probe incorporating a digital readout, with voltage readings from the terminals appearing thereon when the jacks are touched.
Still other systems are illustrated in the April 1986 issue of Motor Magazine. On page 13 is an advertisement for a device manufactured by Thexton Manufacturing Company, of Minneapolis, Minnesota. This system also employs a test probe that is selectively touched to terminals on a matrix board, with readings appearing on a digital meter. The system is also described in an advertising leaflet entitled "How to discover the electronic secrets of Ford's EEC-IV: Introducing Thexton's No. 126 Ford EEC-IV Breakout Box".
Other diagnostic test systems are manufactured by Sun Electric Corporation of Crystal Lake, Illinois and marketed under the name TestLink; by Microtron Products, marketed under the name Autodata Model 840 ECM; and Micro Processor Systems, marketed under the name Analyst 1.
As a result of a patentability search conducted in June of 1986, applicant has become aware of the following issued patents relating to various types of test fixtures and equipment, described herewith.
U.S. Pat. No. 4,220,912 shows a tester circuit that connects to the wiring harness and associated external components of the cruise control circuit for a motor vehicle. Multiple light-emitting diodes are employed, to verify continuity through the wiring harness and various coils associated with the circuit. Also, proper operation of a number of switches can be confirmed. This test circuit is installed in place of the cruise control "computer" module, as opposed to being inserted between a control module and a harness.
U.S. Pat. No. 4,031,461 illustrates a fault detector that can diagnose faulty resistances in a circuit, shorted or open circuits, and other types of malfunctions such as incorrect wiring. This system is of the "single point" type, requiring manually touching a probe tip to various junction points in the circuit.
U.S. Pat. No. 4,366,434 illustrates a combined voltage detector and continuity detector; the operation is briefly explained in column 4, lines 17-32 of the patent specification.
U.S. Pat. No. 4,550,287 illustrates a test instrument employing paralleled light-emitting diodes and series-connected incandescent bulbs. The circuit is intended for use as either a point-to-point continuity checker or a voltage monitor. Selection of the desired function is made by operation of the push button switch.
U.S. Pat. Nos. 4,385,272 and 4,491,781 involve different types of cable testing circuits. U.S. Pat. Nos. 3,559,200 and 3,317,825 describe test modules for three-wire circuits of the type incorporating a hot lead, a neutral lead, and a ground lead.
None of the patented devices identified above is concerned with test modules for use with an automobile's Electronic Control Module (ECM). While the cited patents show a wide range of individual circuits, they would clearly not be useable in their existing form for diagnostic work in connection with a vehicle's ECM and electrical system, and accordingly are considered to be of only passing interest.
It is believed that the main drawback of the automotive diagnostic test systems that have been described is that they tend to be complex in their construction, expensive to manufacture, and difficult to use. More often than not, there is required a good deal of training of the service technician prior to performing any useful troubleshooting work. In addition, while there may be some merit to the concept of hooking up an automobile, via telephone lines, to a central manufacturing facility through the use of a computer, by its very nature a program employing this type of equipment prohibits "road testing" of the vehicle. That is, the vehicle must remain stationary and be physically located in the dealer's service department while any diagnostic tests are being performed and evaluated.
Further, there often exists the possibility of a short-circuit or the occurrence of an overvoltage condition in one of the systems communicating with the ECM; when this occurs, the ECM output circuit may not be capable of sustaining the short or overload, and permanent damage to the unit (ECM) frequently would occur. Under such circumstances, it would have to be discarded completely, and a new, substitute ECM installed. If the location of the short-circuit or overload could not be located, and a substitute ECM is installed, there is the likelihood of the replacement ECM being similarly damaged by the same short-circuit or over voltage condition. As noted above, the recently developed ECM devices are relatively sophisticated, and the expense involved in discarding a unit from inadvertent damage is cost prohibitive.
To the best of my knowledge, attempts to measure current flow between the various terminals of the ECM and the accessory equipment to be controlled were cumbersome, because they usually involved current limiting means, to avoid damage to the ECM. Such limiting means would have to be of the type that did not interfere with the operation of the ECM. It does not appear at present that a satisfactory solution to this problem has been proposed, in terms of maintaining reliable operation without excessive cost or the use of relatively complex circuitry.
Further, it is well established in the electronics field that electrical malfunctions that are of an "intermittent" nature are the most difficult to trace. When one considers the additional variables resulting from vibration, jarring, etc. of a vehicle while it is being driven, coupled with the requirement that during road testing at least two people are needed, one to drive the vehicle, and the other to search for the problem or malfunction, it can be readily appreciated that great difficulty is faced by service personnel in locating and repairing faults whose symptoms appear only during performance of the vehicle under actual driving conditions. To my knowledge, the capability of checking a vehicle during "road testing" has been completely ignored in virtually all of the vehicle diagnostic systems noted above.
Also, while the use of test probes and insulated terminals mounted on matrix boards is satisfactory for laboratory or service station work, it is not at all suitable for road testing, since it generally requires the use of both hands of one of the service technicians while he attempts to simultaneously read a digital voltmeter or equivalent device.
Finally, in many of the known test systems, either the cables are too short to permit a hand-held probe box to be extended into the passenger compartment, or the required vehicle connections do not lend the unit to use while the vehicle is being driven. Road testing is thus impossible.